Field of the Invention
This invention relates generally to methods and apparatus for mounting a tread ring onto a tire carcass or casing.
Description of the Related Art
It is known to mount treads onto buffed tire casings during tire retread operations. For example, tread strips may be wrapped around a tire carcass until the tread ends generally meet at a joint, whereby elastomeric joining material is applied to fill any gap between the opposing terminal ends. The terminal ends may be stapled to retain the arrangement. This often results in an uneven, aesthetically unpleasing joint.
By further example, a tread ring may be expanded by a plurality of fingers spaced about the tread ring's underside. The tread ring is expanded beyond the outside diameter of the tire carcass, the expanded tread ring generally forming a polygon representing the finger arrangement. After elastomeric joining material is arranged between the tread ring and the tire carcass, air cylinders then force the tread ring onto the tire carcass. The fingers are then removed laterally from the retreaded tire carcass. The existence of fingers arranged between the tread ring and the tire carcass and the localized stretching arising therefrom can cause localized abnormalities, such as localized alterations to the tread ring and discontinuous application or presence of joining material along the underside of the tread. Such abnormalities may hinder tire quality and performance.
Another exemplary process for mounting a tread ring utilizes centrifugal forces to expand the tread ring during a spinning operation. Once the tread ring expands, the tire carcass is inserted centrally. Thereafter, the rotational speed of the tread ring is slowed until the tire is mounted onto a carcass spinning at a similar speed such that there is little if any relative rotation between the tread ring underside and the outer surface of the tire carcass. Because there are imbalances inherent in each of the tread ring and the tire carcass, rotation of each produces inexact shapes as the imbalances act upon each rotational body, which results in a less-than perfect assembly and interface between non-symmetrical components.
In yet another exemplary process, an uncured (i.e., green) tread is arranged about a buffed tire casing and subsequently put into an annular mold to cure. This method is very expensive, whereby a specific mold is generally required for each tread design or sculpture. Such methods generally produce a lower volume of retreaded tires in comparison to other methods.
Accordingly, there is a need to provide improved methods and apparatus for mounting a tread ring onto a tire carcass.